Agricultural seeders are typically provided with large bulk seed hoppers that carry the supply of seeds or other materials to be deposited in the soil as the seeder traverses a field. As the volume of seeds in the hopper diminishes, the hopper becomes progressively lighter and lighter, which produces several outcomes. For one thing, it means that seeds are in fact being distributed from the hopper, but that fact alone does not mean that they are being distributed at any particular rate, i.e., it does not mean that they are being distributed at the intended rate. Moreover, it means that at some point in time, the hopper will be depleted, but the mere fact that they are being depleted does not provide information as to when such depletion will occur.
In multi-section cultivation seeders having a main section and one or more wing sections, each section is typically provided with its own set of compaction wheels that are located between cultivators at the front of the machine and openers at the back of the machine. The compaction wheels serve the dual purpose of providing rolling ground support for the seeder during its traverse of a field and compacting the soil turned over by the cultivators so it is in the best condition for engagement by the trailing openers. The main section carries the hopper; thus, as the seed supply diminishes in the hopper, the weight of the hopper diminishes and the down pressure applied against the ground by the compaction wheels on the main section likewise diminishes. However, the compaction pressure applied by the wing section wheels is unaffected by changing conditions on the main section and thus soon becomes greater than that of the main section compaction wheels. This non-uniform compaction pressure across the width of the machine can produce a number of undesirable outcomes including, for example, unequal planting depths and uneven seed emergence.
Accordingly, the present invention advantageously utilizes the decreasing weight of the seed hopper due to diminishing seed supply to perform one or more valuable control functions on the seeder in response to such change. For example, the decreasing weight can be used to calculate the actual amount of product applied over a given area, which is then compared with the intended amount. If the deviation between the two values is greater than a set point, an error message can be displayed at a monitor on the tractor to inform the operator. Another function is to calculate and display the estimated time of depletion, based upon the rate of depletion determined by comparing the weight at known time intervals. A further function is to reduce the down pressure applied by compaction wheels on one or more wings of the machine as a function of the decreasing weight of the hopper (and consequent decreasing down pressure applied by the main section compaction wheels) in an effort to maintain uniform compaction wheel pressure across the entire width of the machine. In a preferred embodiment of the invention, the instantaneous weight is sensed by load cells that mount the hopper on the main frame section. A controller receives weight signals from the load cells, along with signals from a pressure transducer that senses instantaneous wing cylinder hold down pressure, processes the signals and causes appropriate reduction in the wing cylinder hold down pressure.